07/02/2005 FCST: Central/Northern Plains

[Mike Hollingshead]

http://www.wxcaster.com/modelskewt.php3?mo...&STATIONID=konl

Interesting setup for nc NE on Saturday. I'm thinking this could be a fairly big day, if not just one nice monster supercell dropping south. That sounding shows 7500 cape, but have been shown other soundings only showing 5000. Not that that matters as it's fairly clear there will be plenty. Not only that, but there is some really damn lovely shear, imo. NW flow at 500mb of 35 knots atop sse sfc flow of 15 knots. Toss in a boundary that runs n/s and doesn't have crazy convergence, but enough with high temps and I am very much game for this one. To me it is screaming isolated sup/s dropping south. Thought I'd start this for anyone brave enough to actually post forecast thoughts on here.

 

[mikegeukes]

Interesting difference in forecast soundings, for example the CAPE, on Earl's site is much higher than the forecast sounding from Plymouth State College and the Storm Machine

Plymouth State College (CAPE much lower than Earl's)
http://vortex.plymouth.edu/cgi-bin/gen_grb...el&size=640x480

Storm Machine (Do not know if this link will work) (CAPE much lower than Earl's_
http://weather.admin.niu.edu/chaser/tempgif/31586.GIF
http://weather.admin.niu.edu/machine/fcstsound.html

College of Du Page Forecast Sounding (CAPE similar to Earl's)
http://weather.cod.edu/fsound/fsoundview.p...&lon=&site=KONL

Mike

 

[Justin Walker]

This day is definately worth watching out for over the next 48 hrs...One thing to remember, the models begin to struggle with the transition from spring to summer, very inconsistant. Although we are not playing with a big ridge here, just something to remember...

Anyways, there will be a enough deep layer shear to support some nice rotating sups, if sfc winds stay backed, then probably enough low level shear to see some tornadoes. Fairly low lcl's will be nice. Boundary in play appears to be a fairly strong dryline...like said earlier, decent convergence. 700hPa temps are a little toasty, about 12C across central Nebraska with a little cooler temps across ne KS. The best vertical motion appears to be across ne KS. It will be interesting to see where the best moisture will setup.

Patiently waiting...

 

[Mikey Gribble]

I really like the setup except for the low probability of a storm. The only problem is going to be the cap. If we can get a storm to fire though, it could be a good chase day. I am some what optimistic because of the added potential for an outflow boundary from overnight convection to increase convergence along the dryline. I will be chasing on Saturday if it looks like there is a reasonable chance of getting a storm. SPC doesn't seem convinced that it is going to happen, but I don't think anybody is going to have a clue what to expect until Saturday morning. I will post a forecast (or at least what I think is a forecast) tomorrow once I have a chance to take a closer look at things.

 

[Anthony Silver]

I agree, the setup looks fairly decent for Saturday, but the 700mb >14C cap will be a challenge to overcome IMO, but this is something worth monitoring.

 

[Mike Hollingshead]

12z eta has 700mb temps of 10-11c at 0z along the boundary. To me this seems like a great cap to have. 0z eta had convective temp of 92 at ONL while the 6z maintains it at 91. 12z eta coming in now and still looks good to me for around O'Neill NE, perhaps nw to start. Southerly sfc flow will be more than adequate with that flow aloft.

 

[Glen Romine]

I see that the morning NAM run is more agressive with developing precip along the dryline, as well as having a well timed 500 mb shortwave passing over the area. 700 mb RH fields suggest the model has considerable lift all the way south to western KS to potential support a broken line of storms. Possible fly in the ointment is the tendency for NAM to overmix the eastward progress of the dryline - so this could leave the actual surface boundary much further west, where the capping inversion will be much stronger, LCL higher and low-level shear weaker and if the wave is correctly timed then it will possibly emerge too soon to aid in convection further west. Regardless, there seems to be plenty of reason to follow this system's potential for at least generating supercells somewhere in the Great Plains tomorrow.

Glen

 

[Steve Miller TX]

I'm getting ready to head out from the DFW area to stay overnight in Liberal or Dodge City...Hays if I have the time. I am in total agreement with Mike H. for tomorrow and I see a good possibility for a couple of intense supercells to sprout anywhere from central regions of NE down into W KS. I like the area around Belleville, KS based strictly on model data and the trends. I'm sure things will change with the 00Z runs.

I've seen caps alot stronger than this busted with good dryline convergence. Given that the potential instability will be pretty volatile, once a weak spot is found in the cap, it'll be party time. With the forecast CAPE values in place, the vertical wind profiles look really great. As a storm starts moving more SE, the "eyeball" SRH values look pretty awesome to me. I'm pretty excited about it myself.

 

[Philip Flory]

Im in agreement with a NW KS/SC NE target for tomorrow afternoon. 12z NAM is indeed much stronger with forcing towards 00z for convection, I am interested to see how the 18z-00z runs stack up against this. I like the same general area as Steve.. possibly a bit more west towards the Norton, KS area.. I also like the area in C NE. Wind fields are very sufficient for supercells .. tornado theat should increase thru the evening with lowering LCL's. 30-35kt mid-layer flow coupled with NW flow would allow a ESE/SE movement of convection into the higher SRH. This is of course all dependent on convection breaking thru.

Anyone notice how the SPC has completely dismissed the NE/KS setup on the new day 2? Edwards on the 6z made mention of the area.. the new outlook fails to even mention the setup.. away from brief mention in synopsis.... seems latest SPC wants to blow off the new 12z NAM.

 

[Steve Miller TX]

I was actually pretty shocked by the SWODY2 until I noticed who wrote it.
That's all I'll say about that. :wink:

I'd say that it warrants a slight risk down into W KS...especially since now the 12z NAM wants to break out precip into that area...an area ripe for violent supercells.

I'm gathering my chase gear for what will likely be my last chase for the season until fall. I'll be heading up through the eastern TX PH into SW KS just in case there is something that pops up worth taking the lens cap off. I'm looking forward to it! I guess I'll see ya'll in the inflow. 8)

 

[Justin Walker]

Anyone notice how the SPC has completely dismissed the NE/KS setup on the new day 2? Edwards on the 6z made mention of the area.. the new outlook fails to even mention the setup.. away from brief mention in synopsis.... seems latest SPC wants to blow off the new 12z NAM.

I don't exactly know what their reasoning is...their obviously have way more experience then I. Two concerns with this setup are: 1. Cap (but seems to be breakable) 2. Nam might be over-forecasting 500hPa flow (imagine that :lol: ) If you believe the GFS, the deep layer shear may not be sufficient for sups and it does not break out precip. The models are not in agreement, so it is tough to really make a reliable forecast. One thing I have noticed with the Nam with the past few systems is they look good 3 to 4 days out but, with each model run thereafter, it weakens the system (Shear wise). It has had a pretty good handle on moisture of late.

Will be looking for some consistency with the Nam...

 

[Stan Olson]

Sounds like they're not trusting the NAM solution at all. Here's this afternoon's AFD from Sioux Falls, SD:

NOT QUITE SURE WHAT TO DO WITH AFTERNOON/EVNG ON SATURDAY. VIRTUALLY
NO CHANCE OF EVEN BEING CLOSE TO THE SFC-850HPA FORECAST DWPTS SAT
AFTN...WHICH RESULT IN NAM PRODUCING MASSIVE CONVECTIVE OUTBREAK DUE
TO -15/-13 SFC/850 HPA LI WITHIN CWA...BREAKING A FAIRLY GOOD CAP
TO DO SO. GFS ONLY SLIGHTLY LESS OFFENSIVE ON THE MOISTURE
FRONT...BUT KEEPS A BIT MORE CAPPING PREVAILING ACRS S. WHAT IS
OF LITTLE DOUBT IS THE FACT THE THERE WILL BE A GREAT DEAL OF SHEAR
WITH THE BAND OF WESTERLIES ALFT. HAVE A FEELING THAT LLJ IS
OVERESTIMATED AS HAS BEEN FOR MOST EVENTS THIS YEAR...AS REALLY
STRONG WAVE DOES NOT COME OUT UNTIL LATER SAT NIGHT INTO SUNDAY.
IF THE CAP GOES TO ANY GREAT DEGREE...WILL CERTAINLY OPEN THE DOOR
FOR ORGAINIZED CONVECTION...ESPLY ACRS THE NRN CWA.

I think I'll sit this one out as it'd be quite the drive from IL. Good luck to those a tad closer to the area.

Stan

 

[Kyle Masters]

NOT QUITE SURE WHAT TO DO WITH AFTERNOON/EVNG ON SATURDAY. VIRTUALLY NO CHANCE OF EVEN BEING CLOSE TO THE SFC-850HPA FORECAST DWPTS SAT AFTN...WHICH RESULT IN NAM PRODUCING MASSIVE CONVECTIVE OUTBREAK DUE TO -15/-13 SFC/850 HPA LI WITHIN CWA...BREAKING A FAIRLY GOOD CAP TO DO SO. GFS ONLY SLIGHTLY LESS OFFENSIVE ON THE MOISTURE FRONT...BUT KEEPS A BIT MORE CAPPING PREVAILING ACRS S. WHAT IS OF LITTLE DOUBT IS THE FACT THE THERE WILL BE A GREAT DEAL OF SHEAR WITH THE BAND OF WESTERLIES ALFT. HAVE A FEELING THAT LLJ IS OVERESTIMATED AS HAS BEEN FOR MOST EVENTS THIS YEAR...AS REALLY STRONG WAVE DOES NOT COME OUT UNTIL LATER SAT NIGHT INTO SUNDAY.IF THE CAP GOES TO ANY GREAT DEGREE...WILL CERTAINLY OPEN THE DOOR FOR ORGAINIZED CONVECTION...ESPLY ACRS THE NRN CWA.

Gotta say I know Jeff Chapman pretty well, and after talking to him about this, I mostly agree. Like i was discussing with him, into SESD and NCNEB, the cap is there, but with the forecast energy averaged between the Eta and GFS, it's certainly breakable. As a rough estimate, I think we're looking at between 7-11 PM for a bow type echo in SESD spawning from Supercells in a line from NC NEB (O'neill area) to N SD.

I think he summed it up very well when he said:

AFTER DISCUSSION WITH SEVERAL OTHERS...TOSSED OUT NAM SLN...AS
SUPER CONVECTION EFFECTIVELY RUINS THE ENVIRONMENT FOR REMAINDER OF
THE FORECAST FOR SAT NIGHT INTO SUNDAY. SLIGHTLY STRONGER CAP ON
GFS THIS TIME ARND...AND SEEMS THAT WLY PREFERRED FLOW WL BRING
PLUME OF MIXED LYR/CAP THRU AT LEAST NEBRASKA. BEST CHC FOR STORMS
SHUD BE ACRS NRN/NERN CWA DURING THE EVENING...FOLLOWING COLLOCATION
OF UPR DIV Q WITH JET ENTRANCE...AND RESPONSE OF VEERING LLJ.

 

[Kyle Masters]

Well it seems like the SPC is kind of discounting his theory when they said that things would be perfect for an MCS evolving as supercells moved from the Eastern SD region across SE SD into MN, and said that the best threat for isolated tornadoes will be over SE SD.

What? What's that I hear calling?
....It's getting louder....
CHASE DAY!

 

[Justin Walker]

Well after looking at the 00z Nam, looks like SPC saw this one coming by not mentioning Neb or Ks. The cap looks to put a lid on anything developing in this area. Not even the low level jet can get things started in this region. Looks like the chase target would need to be shifted N into S Dak. Still looks like we will get some sups here. 997 sfc low helps out a lot, also getting into a breakable cap up here with 700hPa temps running around 10C. Looks like GFS had a handle on this day more than the NAM....Oh well :roll: